Variable speed pump with non-graduating by-pass valve control



March 25, 1958 M. w. HUBER VARIABLE SPEED PUMP WITH NON-GRADUATING BY-PASS VALVE CONTROL 5 Sheets-Sheet 1 Filed March 16, 1953 I llllllllllllllll] l E Hllllllllllll INVENT OR ATTORNEYS Mamwwwnuber 89 March 25, 1958 M. w. HUBER 2,327,354

VARIABLE SPEED PUMP WITHNQN-GRADUATING BY-PASS VALVE CONTROL 5 Sheets-Shee t 2 Filed March 16. 1953 INVENTOR ATTORNEYS March 25 1958 M. w. HUBER 2,827,854

VARIABLE SPEED PUMP wxcm nowcmnuumc amass VALVE CONTROL Filed March 16,1953 :5 Sheets-Sheet 3 I I V 165 166 o lsv 168 4 3 Q .11 147 I Fie.6

mvENTok MadhewWl-Iuber BY Ami i.

ATTORNEYS United States Patent VARIABLE SPEED PUMP WITH NUN-GRADUAT- ENG Bil-PASS VALVE CGNTRQL Matthew W. Huber, Watertovvn, N. Y., assignor to The ?ew York Air Brake Company, a corporation of New ersey Application March 16, 1953, Serial No. 342,647

8 Claims. (Cl. 103-42) This invention relates to parasite power systems for use on vehicles. It is known practice on airplanes, road vehicles, motor boats and the like to use a pump driven continuously by the vehicle-propelling engine to energize a hydraulic system which furnishes the power needed to operate flaps, ailerons, rudders, hatches, landing gears and a variety of other accessory devices.

The invention is adapted to these uses. it will be here discussed as applied to steering automobiles, because that field develops its major possibilities, and imposes some strict, and heretofore troublesome, limitations.

Steering gears commonly include a double-acting booster motor of the open center, follow-up-valve type. A booster motor is piloted by the follow-up-valve, and commonly is proportioned to do /3 to of the work leaving a residuum requiring manual effort and affording what the art calls feel. An open-center valve is one that has a neutral position in which it connects pressure and discharge, and so unloads the pump which energizes the system. See for example Stephens 2,359,802, October 10, 1944. A follow-up-valve is one including a manually movable element (say the valve proper) and a follow-up element (say the valve seal) which is moved by the controlled motor, so that motion of the valve initiates motion of the motor and this in turn causes the seat to overtake the valve. In such an open-center follow-up-valve the seat and valve re-establish the open-center connection when the seat overtakes the valve, so that as soon as the motor has completely responded to any setting of the manually movable element the pump is unloaded at the valve.

This is a known arrangement. It has definite limitations. In a pleasure car silent operation is essential, the system must be operative at idling speeds of the engine and must be controllable smoothly under road conditions involving engine speeds ten or more times the idling speed. It must not heat.

One cause of noisy operation is heavy unloading circulation through the open-center. The open-center necessarily involves throttling and eddying which, when the flow is heavy, cause both noise and heating. Open-center unloading, when used as the main unloading path, imposes limitations on the unloading control, particularly where pump speed is widely variable. In the prior art a palliative has been used, and comprises a graduating un loader valve local to the pump, and made responsive in one way or another to the rate of flow through the opencenter.

The present invention provides a large-capacity unloading valve, local to the pump, but so designed as to be either open or closed. It is inherently non-graduating. It has no biasing spring. Instead the unloading valve is shifted full stroke by a sensitive differential pressure motor (conveniently a differential piston motor), which moves in reverse directions as flow through the open-center rises and falls past a critical value.

The effect is remarkable. Open-center flow can be reduced to a moderate pilot rate and the unloader valve ice local to the pump becomes the main unloading means. The system operates silently. There is remarkable freedom from heating. The pump size can be reduced with saving in power consumption and wear.

Tests of full sized units have been made and demonstrate that residual pressure can be reduced from 70 p. s. i. to 5 p. s. i. and maximum temperature from 180 F. to F. Contrary to the conditions with the best prior art arrangement known to applicant, the full pump output is available when the pump is loaded. This will certainly lead to reduction in the size of the pump, but only extensive road tests will furnish a final criterion for pump size.

Successful embodiments of the invention will now be described by reference to the accompanying drawings, in which:

Figure 1 shows in axial section a pump unit designed for use in automobile steering systems, the pump being mounted within the system reservoir. The view is in axial section on the line 1-1 of Figure 3 and the local unloading valve is shown in loading position.

Figure 2 is a fragmentary view showing the unloading valve of Figure 1 in unloading position.

Figure 3 is a transverse section on the line 33 of Figure l.

Figure 4 is a transverse section on the line lb-4 of Figure 1.

Figure 5 is a diagram of a simple circuit including the pump of Figures 1-4, a pilot valve of the open-center type and a double-acting motor piloted by said valve.

Figure 6 is a view, partly in diagram, showing how the invention may be embodied in a self-contained control valve for use in any circuit including an open-center pilot valve and a positive displacement pump.

Refer first to Figures 1-4 inclusive.

The pump is of the vane type and includes a right circular cylindrical chamber in which a disc-like vaned rotor is eccentrically mounted.

A head plate 8 and a port plate 9 spaced apart by ring 11 enclose the pump chamber. The ring 11 seals at its ends against the plates and is encircled and centered by six bolts 12 which connect the plates 8 and ii and also the flanged end block 13 which overlies the port plate 9.

The head plate and the port plate are each bored to receive a corresponding bearing bushing 14. These bearings are coaxial and support the rotary shaft 15 whose axis is parallel with the axis of the bore of ring 11, but eccentric thereto. A disc-like right cylindrical rotor 16 is splined to shaftlS and confined between snap-rings 17 which seat in annular grooves in the shaft. The eccentricity of the disc is such relatively to the diameters of the disc and the bore of ring 11 that the disc and ring are nearly in contact in the zone of closest approach (see Figure 4).

A shaft seal 18 is mounted in head plate 8 to resist leakage of hydraulic liquid along shaft 15 which extends through and projects beyond the head plate. This liquid iscustomarily a suitable oil, and will be referred to hereinafter as oil. Since steering gear pumps are commonly driven from the fan belt of the propelling engine, the shaft 15 is shown equipped with a pulley 19 mounted on its projecting end and suited for the described use.

Viewed from the port plate end the rotor 16 and shaft 15 turn counter-clockwise, as shown in Figure 4. The periphery of the rotor is slotted at intervals to receive vanes 21 which are conventionally illustrated but may be of any known form, including laminated types. The slots are secant, rather than radial and are inclined forward, but radial arrangements are known and available for use if preferred.

The rotor and the vanes span the interval between and make a running fit with the proximate plane faces of the head plate and port plate and the outer ends of the vanes maintain contact with the inner face of the ring 11.

The discharge port 22 is arcuate and formed in plate 9 in thetr'ace "of the projecting portions" ofpthe :va'nes;

As indicated in Figuresl and 3, port '22 isnarrow on the face that engages the rotor and flares widely 'in the direction of discharge flow. A balancing port groove 23 '13 formed. in 'the'head plate 8 and is va mirror image of a port 22. Branch ducts 24 lead from the discharge port to one of two circular grooves v25 cut in the faces of the rotor and open to the bottoms of the vane slots so that all vanes are biased outward by discharge pressure.

The inlet port 26 is also an arcuate slot in the plate 9 balanced by an arcuate groove 27 in the plate 8.

The pump so far described is an ordinary vane pump,

and so far as the invention is concerned typifies any suitable positive displacement pump. For this service a rotary pump is obviously preferable. One characterized by smooth delivery and low internal losses is desirable, and the illustrated pump offers both theseadvantages.

A passage 28 leads through end block 13 to port 26. It has a connection 29 for the return line of the hydraulic circuit and is in open communication with the oil reservoir at 31. The reservoir is enclosed by the cuplike shell 32 which makes a slip joint with head plate 8 sealed by o-ring 33. The means for retaining shell 32 will be described hereinafter.

From the discharge port 22 a passage leads to a connection 34 for the pressure line of the hydraulic circuit. The connections 29 and 34 are similar and each includes a tubular nipple which passes through a corresponding opening in the base of cup 32 and screws into the end block 13. Each nipple has a nut-like flange which engages the base of the cup and seals it to the end of the end-block 13. A machine screw 35 passes through an opening at the center of the base of cup 32 and holds the cup independently of connections 29 and 34. A toric gasket 36 is used to assure a seal.

In the passage between the port 22 and discharge connection 34 are the by-pass controlling valve and its differential-piston actuating motor. This unit is the crux of the invention.

A portion of the cylindrical bore 37 is reduccd in di ameter by a tubular bushing 38. This is fixed in position by an external flange held in an annular recess in end block 13 by the abutting port-plate 9, A side-port in bushing 38 is connected by by-pass port 41 with inlet Passage 28 nd c ns quently ith otht e re e voir and the inlet port 26. Port41 is of large size, so

that when this port is open the pump is nearly com-,

pletely unloaded.

Port 41 is controlled by a combined valve and differential piston comprising a larger head portion 42 which works in bore 37 and a smaller portion 43 which works in bushing 38. A port 44 vents the annular space at the end of bushing 38 to the interior of the reservoir, which is functionally equivalent to connecting it to port 41 or inlet 26 since all are in free communication. A port 45 of moderate size leads through the valve-piston unit 42- 43. It is convenient, but not strictly essential that this port lead axially through the valve-piston.

. The port 45 is dimensioned to produce, at any operating speed including the lowest, a pressure drop sufiicient to move valve piston 42-.43 outward (leftward in Figure 1) whenever outflow through 34 is subject only to slight back pressure as is the case in the neutral positions of the open-center valve. This motion exposes port 41 and unloads the pump nearly completely. However, if back pressure resisting outflow through connection 34 is developed (as would be the case when an open-center valve controlling outflow is moved to close or restrict the pen-c e the the r sulting in r a pressure ca s ure 1) full strokepnd close port-4 1. This follows from the fact that the increased back pressure acts on both ends of valve piston 42-43, whose outerend has the larger effective area. There is a critical degree of back pressure at which shifts tend to start. The valve then moves full stroke and without graduating action. By graduating action is meant progressive variation of port opening in response to a range. of pressure changes. Of course, friction of the valve and resistance to fluid flows have a tendency to retard shifts and cushion the shift to some degree.

A threaded filling vcap for the oilyrese'rvoir is shown A cartridge-type spring-loaded relief valve, indicated by the numeral 47 connects discharge passage 37 with the reservoir and passage 28 at all times when port is closed. Its function is to relieve overloads and shocks, it has no normal regulatory function.

The essentials of a circuit including an open-center control valve are shown in Figure 5.

A pump of the type shown in Figural-4 'appea'rs'at 51.

The suction line 52. leads to suction connection 29.

The discharge line 53 leads from the discharge connection 3 The valve-seat member 54 has two discharge chambers 55 and 56 each connected to a branch .of suction line 52. Between chambers 55 and 56 is:a supply. chamber 57 to which the high pressure discharge line 53.1eads.

Sweat member 54 has an axial here which intersects the chambers 55, 56 and 57 and receives a balanced piston pilot valve having bore filling end portions58 and 59 separated from a middle land .61 by two reduced portions .as shown. The control edges of end portions 58 and 59 and of middle land .61 are shown with exaggerated clearance as to the seat ports. 7

The booster motor is diagrammed as a double acting cylinder 62 withpiston 63 whose rod 64 is operatively connected with the steering gear. The working spaces of cylinder 62 are connected by lines 65r66 with the valve seat bore, one between chambers 55 and 57 and the other between chambers 57 and 56.

When the pilot valve is centered with reference to seat position of Figure 1 and closes by-pass 41. The same motion of the pilot valve unbalance's the pressures in the two ends of: cylinder 62 so the piston moves and actuates the steering gear. a Q

In conventional steering gears there is a follow-up valve arrangement 'so that motion of piston 63 restores the original positional relation of. the pilot-valve and seat. The effect is as. if piston rod 64 were connected to seat member 54 and caused the seat to follow and overtake the valve. Follow-up valvegears, of many types, are known, and are as old as servo-motors. As to the invention, the significant thing is the use of an open-center valve. That type of valve can be given follow-up characteristics by any of several conventional arrangements, and has been so usedJ Figures 1 to 4 show theincorporation of the invention in a refined type of pump designed for pleasure-car use.

The inventive concept is however available for use with various devices such as graders, bull-dozers, dump trucks, lift trucks, to name a representative few. The system may or may not include a sump, and the pump may be driven in any way. g 4

To emphasize general utility Figure 6 shows the invention included in a typical circuit. Reference numerals" used in Figures .l.-.-5 :butincreased by 10.0 are .used' to identify analogous parts. Fromia sump any1pump' 151 draws oil and delivers it under pressure to line 153. Line 153 supplies high pressure oil to any open-center valve unit 154 through a control valve in housing 113. This comprises a difierential valve-piston 141-143 controlling unloading by-pass 141. The return line 152 leads from valve 154 to sump 100. A relief valve 147 is shown.

The open-center valve unit 154 may be of the type permitting individual control of several motors and has four connections, 165, 166, 167, and 168, which could be connections for two double-acting motors. See the patent to Stephens 2,359,802, October 10, 1944, Figure '1 for a good example of a multiple open-center valve. This valve includes its own pressure relief valve, a fact which would permit elimination of valve 147 shown in Figure 6. However, a relief valve close to the pump is considered desirable for the arrangement of Figure 6, and one is included.

Figures 1-5 illustrate a highly refined application of the invention. Figure 6 indicates its availability when the unloading valve is not built into the pump, and when the open-center valve is of the multiple type capable of controlling several motors. These multiple valves are commercially produced with series hook-ups and parallel hook-ups. The invention can be used with either.

Throughout the specification reference has been made to pumps characterized by variable delivery arising as a result of varying speed of operation. This condition greatly increases the difficulty of effecting satisfactory control, and ability to overcome this difficulty is an important characteristic of the invention, but the invention is not in any sense dependent on the variable speed or variable delivery characteristic of the pump. It can be used to control a constant speed constant delivery pump and operates in the same way in effecting such control.

What is claimed is:

1. A quick-acting unloading valve for interposition between a pump operated continuously, but at varying speed so that the delivery of the pump varies between a minimum and a maximum, and 'an open-center controlling valve, said unloading valve comprising a housing having an inlet for connection to the pump, an outlet for connection to the controlling valve and an unloading port; means affording communication between said inlet and outlet inadequate to pass freely the minimum delivery of the pump; and means affording a valve controlling said unloading port and a differential pressure motor mechanically related thereto to shift the valve between its open and closed positions, said motor comprising connected movable abutments namely a smaller abutment subject to inlet pressure acting in a valve opening direction and a larger abutment subject to back pressure in the outlet acting in a valve closing direction.

2. A quick-acting unloading valve for interposition between a pump operated continuously but at varying speed so that the delivery of the pump varies between a minimum and a maximum and an open-center controlling valve, comprising a housing having alined communicating bores of dilferent diameters, an inlet to the outer end of the smaller bore adapted for connection to the pump, an outlet from the outer end of the larger bore adapted for connection to the control valve, an unloading side port leading from the smaller bore and a vent port leading from the inner end of the larger bore; a difierential piston having connected heads slidable in respective bores, the smaller head serving alternatively to expose and to close said side port as the pistons move toward and from said discharge connection; and means affording a constantly open flow path between said inlet and said outlet said fiow path being inadequate to pass freely the minimum delivery of the pump.

3. A quick-acting unloading valve for interposition between a pump operated continuously but at varying speed so that the delivery of the pump varies between a minimum and a maximum and an open-center controlling valve, comprising a housing having alined communicating bores of different diameters, an inlet to the outer end of the smaller bore adapted for connection to the pump, an outlet from the outer end of the larger bore adapted for connection to the control valve, an unloading side port leading from the smaller bore and a vent port leading from the inner end of the larger bore; a differential piston having connected heads slidable in respective bores, the smaller head serving alternatively to expose and to close said side port as the pistons move toward and from said discharge connection; and means affording a connection between said inlet and said outlet and comprising a continuously open passage leading longitudinally through said differential piston and of such size and length as to develop back pressure on the minimum delivery flow of said pump.

4. An unloading mechanism for interposition between a continuously running pump and an open center controlling valve comprising a housing enclosing a motor cylinder having two co-axial bores of unequal diameters and having an inlet for connection with the pump delivery, an outlet for connection with the controlling valve, and an unloading port which when open unloads the pump nearly but not completely and when closed loads the pump; means affording a valve shiftable between positions in which respectively it opens and closes said unloading port, and a mechanically related double-acting differential piston in said motor cylinder, said piston being subject in a valve opening direction to inlet pressure and in a valve-closing direction to discharge pressure and so dimensioned that when said pressures are nearly equal the piston is forced in a valve-closing direction; and means affording a flow connection between said inlet and outlet suflicient to pass the liquid delivered by the pump with a pressure drop large enough to cause said piston to move to its valve opening position when resistance to discharge through said outlet is below a chosen value.

5. A quickacting unloading valve for interposition between a continuously operating pump and an opencenter controlling valve, said unloading valve comprising a housing having an inlet for connection to the pump delivery and an outlet for connection to the controlling valve, and an unloading port; means affording communication between said inlet and outlet and dimensioned to develop a relatively low back pressure when the pump is operating and the unloading port is open; and means affording a valve controlling said unloading port and a differential motor mechanically related thereto to shift the valve between its open and closed positions, said motor comprising two mechanically related movable abutments, namely a smaller abutment subject to pressures developed in the inlet and urged thereby in a valveopening direction and a larger abutment subject to back pressures developed in the outlet and acting in a valve closing direction.

6. A quick-acting unloading valve for interposition between a continuously operating pump and an opencenter controlling valve, said unloading valve comprising a housing having alined communicating bores of different diameters, an inlet to the outer end of the smaller bore adapted for connection to the pump delivery, an outlet from the outer end of the larger bore adapted for connection to the control valve, an unloading side port leading from the smaller bore and a vent port leading from the inner end of the larger bore; a differential piston having connected heads slidable in respective bores, the smaller head serving alternatively to expose and to close said side port as the pistons move toward and from the discharge connection; and means affording a continuously open connection between said inlet and outlet and comprising a passage extending longitudinally through said dilferential piston and dimensioned to afford a small back pressure when the side port is exposed and the pump is operating.

7. A pump unit for use in hydraulic circnits of the parasite power type in which the parasite motor is controlled by an open-center valve and the pump is driven at varying speeds by the propelling engine of a vehicle, said unit comprising a rotary vane type pump adapted to be driven by an engine and having inlet and discharge connections and, a large capacity by-pass between said connections and within the structure of thepump; and a quick acting valve controllingsaid by-pass, mounted in said discharge connection and including means defining in said connection alined communicating bores of diiierent diameters the. smaller being at the entrance end and the larger at the discharge end and the smaller having a side port leading to said by-pass, there being a vent port from the inner end of the larger bore, and a difierential piston having connected heads slidable in respective bores, the smaller head controlling said side port as the piston moves, said differential piston having a continuously p passage lead ng ngitud nal y the et gh and of such size as to develop back pressure at the minimum delivery flow from said pump. a i

S. A pump unit for use in hydraulic circuits of the parasite power type in which the parasite motor is controlled by an open-center valve and the pump is driven at varying speeds by the propelling engine of a vehicle, said unit comprising a rotary vane type pump adapted to be driven by an engine and having inlet and'discharge connections and a large capacity bypass'between said connections and within the structure of the pump; a

quick acting valve controlling said by-pass, mounted in said discharge connection and including means defining in said'conne'cti on alin'ed communicating bores of difierent diameters the smaller being at the entrance end and the larger at the discharge end and the smaller having a side port leading to said by-pass, there being a vent port from the inner end of the larger bore, and a diiferential piston having connected heads slidable in respective bores, the smaller head controlling said side port as the piston moves, said differential piston having a continuously open passage leading longitudinally therethrough and of such size as to develop back pressure at the minimum delivery flow from said pump; and an oil retaining reservoir attached to said pump and surrounding a major portion thereof, said pump inlet and said vent port being in free communication with the interior of said reservoir,

ReferencesCited in the file of this patent U ITED ST E PA 976,917 Richards Nov. 29, 1910 1,110,567 McAulay Sept. 15, 1914 1,980,404 Harman et al Nov. 13, 1934 2,212,833 Huber Aug. 27, 1940 2,241,665 Herman May 13, 1941 2,724,335 Eames u Nov. 22, 1955 2,737,966 Lucien Mar. 13, 1956 2,742,862 Banker Apr. 24, 1956 

